Meaning

noun steadiness of mind under stress

noun wind moving at less than 1 knot; 0 on the Beaufort scale

verb make calm or still

originFrom Middle English calm, calme, from Middle French calme, probably from Old Italian calma, of uncertain origin. Calma may derive from Late Latin cauma (“heat of the midday sun”), from Ancient Greek καῦμα (kaûma, “heat, especially of the sun”), from καίω (kaíō, “to burn”), or possibly from Latin caleō. Compare also Lombardic *chalm, *chalma (“frozenness”), ultimately from Proto-Germanic *kalmaz…

Etymology from Wiktionary, CC BY-SA 3.0